Cohesion theory

Magnetic fields are capable of generating, even at modest flux densities, i.e. less than one tesla. Important interactions with flow and structural phenomena. Since the magnetic force is often considerably less than force magnitudes associated with forced and natural convection in liquid electrolytes, classical MHD theory cannot be employed exclusively to explain all experimentally observed magnetic field effects. On the other hand, there exists at present no other cohesive theory for the treatment of electrlc/magnetic phenomena in liquids. The current lack of a comprehensive framework of analysis remains a serious challenge to all theoreticians, be they mathematicians, physicists or chemists. 

The problem of elucidating the mechanisms of transport in the various parts of the transport network has been treated in the past in a compartmentalized manner. As regards the question how considerable volumes of water with dissolved nutrients reach the leaves, the cohesion theory " " postulates that the evaporation of water from the surface of leaves (transpiration) provides the driving force. As the radius of the xylem conduits is too large for the capillary action to be of much help negative... 

Fig. 219. An experiment to demonstrate the cohesion theory of transport in the xylem. Transpiration from a block of plaster or a twig causes mercury to be sucked up into a glass tube (from Walter 1962).

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